1. Field of the Invention
The present invention is generally related to an adjustable pitch propeller and, more particularly, to a propeller that comprises a hub portion to which a plurality of propeller blades can be attached in such a way that the pitch of the blades is manually selectable.
2. Description of the Prior Art
Those skilled in the art are familiar with many different types of variable pitch and adjustable pitch propellers. Some of these propellers are capable of automatically adjusting the pitch of the propeller blades while the propeller is rotating and providing the propulsion for a marine vessel. Other types of propellers are manually adjustable. In all types of variable pitch and adjustable pitch propellers, the relative positions of the propeller blades to the propeller hub can be changes, either automatically or manually.
U.S. Pat. No. 5,527,153, which issued to Bernhardt on Jun. 18, 1996, discloses a variable pitch propeller for a power boat. Three blades are mounted on a housing which is carried by the propeller shaft. Each blade has an axle received in the housing. Each axle has a slot receiving a dowel carried in the housing so the blade can rotate approximately 5.degree. between two pitch positions. A centrifugally-operated, spring biased latch carried in the housing locks the shaft in each pitch position. The blade is released from the latch by a predetermined change in the hydrodynamic force acting on the blade surface. The propeller shaft is connected to the propeller assembly by three plastic keys which shear to permit the propeller assembly to spin with respect to the propeller shaft when the propeller assembly strikes a predetermined resistance, such as a rock or the like.
U.S. Pat. No. 5,445,497, which issued to Seemar on Aug. 29, 1995, describes variable pitch propellers. The variable pitch propeller is intended for use with a marine vessel and it includes a hub for mounting on a driven shaft. The hub has a plurality of blades which are mounted to bearing rings which are carried in recesses in the hub, with removable snap rings retaining the bearings therein with cap screws from the bosses extending to and engaged with the bearing rings for full rotation to automatic pitch positions and with cap screws which may extend into spaced holes in the hub for setting the blades to desired fixed positions.
U.S. Pat. No. 5,022,820, which issued to Bergeron on Jun. 11, 1991, discloses a variable pitch propeller which includes a central hub defining an axis of propeller rotation and a plurality of blades connected to and extending from the central hub. Each blade is mounted for rotation about a pitch axis. A cam mechanism is provided to translate centrifugal forces imposed on the blade into a force which tends to rotate the blade toward a course pitch. That force is opposed by water pressure tending to decrease the blade pitch. The cam mechanism includes a cam groove formed in an insert and made of a material that is harder than the blades. The propeller is provided with variable minimum and maximum pitch stops. A resilient bias is provided toward minimal blade pitch.
U.S. Pat. No. 5,232,345, which issued to Rocco on Aug. 3, 1993, describes a feathering propeller with a manually adjustable pitch. This device performs a pitch adjustment in a feathering propeller by employing a planet gear engagement between a pinion hub keyed on the driveshaft and planet pinions at the base of the blades of the propeller which are rotatably mounted through holes of the wall of the hub's casing. This is accomplished by registering the relative angular position of a second portion of the casing with respect to the first portion of a casing housing the planet gear. The registration of the pitch takes place by parting the second portion of the casing from the first portion against a resistance of a push-back spring for a distance sufficient to disengage a coupling between the second portion and first portion of a casing or the pinion hub, rotating the second portion to the point of disengagement with respect to the first portion of a casing before releasing the pull causing again the engagement of the two portions in a modified relative angular position. In this way, the stop mechanisms for the travel of a dragging sector solidly connected to the hub of a propeller, which are substantially formed on the internal wall of the second portion of the casing, change their relative position about the sector thus modifying the limit orientation assumed by the blades when the drive shaft is rotated. Resilient elements are used between abutment surfaces for preventing deformation thereof.
U.S. Pat. No. 5,290,147, which issued to Karls et al on Mar. 1, 1994, describes a variable pitch marine propeller with a shift biasing and synchronizing mechanism. The propeller includes a hub which is rotatable along a longitudinal axis and which has a plurality of blades extending radially outward therefrom. The blades are pivotable about respective radial pivot axes between a low pitch position and a high pitch position. A disc has a plurality of guide slots which each receive and retain a respective lever arm extending rearwardly within the hub from a respective blade. A biasing spring coaxial with the longitudinal axis of rotation of the hub biases the disc to bias the levers arms and blades to the low pitch position. The disc is a generally flat planer member extending radially outward from the longitudinal axis at the rear of the hub and includes a preload mechanism accessible at the rear of the hub for adjusting the bias. The disc restricts movement of the lever arms along the guide slots such that the lever arms can move only in unison, which prevents blade flutter. Pivoting of the blades is controlled by movement of the lever arms along the guide slots and arcuate movement of the guide slots as the disc rotates about the longitudinal axis, such that pivoting of each blade from its low pitch position to its high pitch position requires both a movement of the respective lever arm along its respective guide slot and rotation of the disc to arcuately move the guide slot.
U.S. Pat. No. 5,226,844, which issued to Muller on Jul. 13, 1993, describes an actuator for a variable pitch propeller. A drive for a boat is provided with a propeller hub which is rotatable about a main axis extending in a normal travel direction, a plurality of blades projecting generally radially of the main axis from the hub and each being pivotal so as to be of variable pitch. The respective blade rods extend axially and are displaceable axially relative to the hub in order to vary the pitch of the blades. The stator carried on the boat downstream in the direction from the hub and nonrotatable about the axis rotatably supports a cylinder housing that is releasably connected to the rods for joint axially movement therewith. A piston is displaceable along the axis in the cylinder and is releaseably connected to the hub for joint axial movement therewith. Pressurizable lines extend through the stator and are connected to the cylinder for alternately pressurizing the piston and thereby relatively axially shifting the rods and hub.
U.S. Pat. No. 5,073,134, which issued to Muller on Dec. 17, 1991, discloses a boat drive with an adjustable pitch propeller. The boat drive is of the type in which a housing outside of the hull of the board and below the water level receives a hollow propeller shaft driven by a drive shaft connected to the propeller shaft by a transmission. The hub of a variable pitch propeller is mounted on the propeller shaft and the axially extending stems which adjust the pitch of the hub are engaged by a push rod extending through the prop shaft and connected to a double acting cylinder at the opposite end from that at which the rod is connected to the stems.
U.S. Pat. No. 4,973,225, which issued to Kruppa on Nov. 27, 1990, discloses an adjustable propeller. The controllable pitch propeller has a driven rotating hub and adjustable propeller blades positioned therefrom. An adjustment device is provided which has an adjustment ring that can move axially and which has adjustment bars attached to it for adjustment of the propeller blades. At least one continuous waste gas channel is positioned in the hub. In order to relieve the hub of external adjustment forces, the adjustment ring is constructed as a cylinder piston which is movably axially positioned in a cylinder chamber of the hub which can be acted upon hydraulically on both sides.
U.S. Pat. No. 5,017,090, which issued to Morrison on May 21, 1991, describes variable pitch blades and a mechanism for driving them. A propeller blade is provided with a planer configuration, an inner end portion, an outer end portion, a relative sharp outwardly swept back leading edge portion, and a cylindrical stub axially aligned with the plane of the blade and affixed to the inner end portion of the blade. A mechanism enables the pitch of the blades to be adjusted by the operator through a continuum of positions ranging from fast forward to fast reverse so that the boat can be operated at a full range and variety of speeds and can be stopped rapidly. It can also be maneuvered with precision. The mechanism can be used for operating flat-bottom boats in swamps, shallow water, bayous, lakes, rivers and the like, and pass through wet mud and swampy marshes choked with mud or vegetation without excessively fouling the propellers. The mechanism can be serviced and repaired easily and quickly and can be employed to operate small craft such as mud boats with a minimum loss of interior boat space.
U.S. Pat. No. 4,929,201, which issued to Pitt on May 29, 1990, describes a variable pitch marine propeller system. The propeller comprises two removable symmetrical propeller blades with cylindrical bases each having a drive lug attached proximate the driving edge of the point of attachment of each blade. A coupling is associated with the drive lugs of the bases and structured to hold the blades by the bases to align and simultaneously rotate the pitch of the blades in equal and opposite directions in response to movement of the coupling. A hub sub-assembly encases the coupling and bases of the blades to allow the blades to pivot and assume a forward or rearward pitch. The hub sub-assembly has a front end and a rear end capable of mounting on a drive shaft. A spring is associated with the coupling to initially position the coupling in a position which holds the blades in a rear pitch configuration. A hydraulic piston system is associated with the coupling means to provide a predetermined fixed pressure on the coupling to alter the space pressure and move the coupling to a position which causes the blades to assume the desired forward or rearward blade pitch.
U.S. Pat. No. 4,540,341, which issued to Wuhrer on Sep. 10, 1985, discloses an adjustable propeller for marine vessel drive applications. The propeller has an adjusting mechanism for adjusting the pitch of the individual propeller blades. The mechanism comprises an actuator and a correction mechanism for each propeller blade for cyclically adjusting the pitch angle of a related propeller blade under the control of a control device.
U.S. Pat. No. 5,733,156, which issued to Aihara et al on Mar. 31, 1998, discloses a variable propeller for a boat. Variable diameter main blades and stationary subsidiary blades are mounted on a propeller boss in order to provide further enhanced low-speed diving properties and high-speed and high-output performance. When the main blades are in closed positions in which the propeller diameter assumes a minimum value, the main and subsidiary blades are axially superposed on each other. When the main blades are in opened positions in which the propeller diameter assumes a maximum value, the main and subsidiary blades are arranged in a relation such that their blade surfaces are substantially in line with each other.
U.S. Pat. No. 4,297,079, which issued to Marshall on Oct. 27, 1981, describes a variable pitch marine propeller which has a plurality of circumferentially spaced blades mounted on axles at the root portion of the blades in a hub to permit independent movement of each of the blades about an axis of rotation which is substantially parallel to the axis of the hub. The blades can move between a first nested position adjacent the hub and a second extended position. Each of the blades includes leading and trailing striking surfaces or root segments on the root portion of the blades which are hub engageable upon initial rotation of the blade in either direction. Intermediate the leading and trailing segments of the blades are positioned cushioning means which may be mounted in either the hub or the blade root segments for inhibiting the shock of engagement of the blades and the hub upon initial start up of rotation of the hub or upon a sudden reversal of rotation of the hub. The cushioning means includes water entrance and graduated exit means with means to capture water therein to act as a shock absorber for the blades against the hub.
U.S. Pat. No. 4,150,921, which issued to Wennberg et al on Apr. 24, 1979, describes a marine propeller system with adjustable pitch and axially removable blades. Marine propellers are constructed with a split-hub design, permitting adjustment of the pitch of the blades, and axial removability of the blade. By virtue of the axial removability of the blades, the blades can be removed easily for repair or replacement without increasing the diametrical clearance between the blade tips and a tunnel or nozzle of the type in which propellers are frequently disposed. Also, individual blades can be removed without the necessity of dropping the rudder, which is necessary in many vessels utilizing solid propellers. The blades have their spindles or roots clamped to the hub such that axial adjustment of pitch can be achieved by reducing the clamping force. The hub preferably is formed in two sections, with one section being mounted to or forming part of the propeller shaft and including recesses which partially house the blade spindles or roots. The other section preferably is made up of a plurality of independently removable clamping segments, each of which is formed with a recess which cooperates with a recess in the first section to house a blade spindle and to clamp the spindle in a fixed blade pitch position. By removal of a selected clamping segment, its blade can be removed axially rearwardly without necessitating substantial diametrical clearance at the blade tips. Bolted connections are used between the clamping segments and the first section of the hub so as to facilitate both pitch adjustment and blade removal.
All the patents described above are hereby explicitly incorporated in this description by reference.
Propellers which are adjustable or variable often require significant complexity of the associated mechanism. As a result, the cost of the adjustable propeller is often much higher than the cost of a similar propeller which is not adjustable. It would therefore be significantly beneficial if an adjustable propeller could be provided which relies on a simple mechanism that allows an operator to manually change the pitch of the blades in a manner which is accurate and repeatable.